As discussed in certain commonly-assigned, co-pending, published U.S. patent applications related to wavelength dispersive x-ray fluorescence (XRF) systems, the use of monochromating optics in the excitation and/or detection paths provides various advantages, including the ability to narrow the spectrum of wavelengths present at the sample under analysis, thereby increasing the signal-to-background ratio of the system and improving analysis results (e.g., see U.S. application No. 60/336,584 filed Dec. 4, 2001, and entitled “X-Ray Tube and Method and Apparatus for Analyzing Fluid Streams Using X-Rays,” perfected as PCT Application PCT/US02/38792-WO03/048745, entitled “X-Ray Tube and Method and Apparatus for Analyzing Fluid Streams Using X-Rays;” and U.S. application No. 60/299,371 filed Jun. 19, 2001, and entitled “XRF System Including Focusing Optic on Excitation Side and Monochromatic Collection,” perfected as PCT Application PCT/US02/19272-WO02/103710, entitled “Wavelength Dispersive XRF System Using Focusing Optic for Excitation and a Focusing Monochromator for Collection” all of which are incorporated by reference herein in their entirety).
Similar benefits of such monochromatization can also be applicable to other types of x-ray analysis systems, including, for example, x-ray diffraction systems depending on the particular application. Though not directly addressing monochromatization, advanced diffraction systems are addressed in, for example, commonly assigned U.S. application No. 60/492,400 filed Aug. 4, 2003 entitled “In-Situ X-Ray Diffraction System Using Sources and Detectors at Fixed Angular Positions,” perfected as PCT Application PCT/US04/25112-WO2005031329 of the same title; and application No. 60/489,047 filed Jul. 22, 2003 entitled “Method and System for X-Ray Diffraction Measurements Using an Aligned Source and Detector Rotating Around a Sample Surface,” perfected as U.S. application Ser. No. 10/893,511 filed Jul. 16, 2004, all of which are incorporated by reference herein in their entirety.
In addition to monochromatic beams, small, intense x-ray beam spot sizes at the sample are also of significant interest in certain x-ray analysis systems. Small spot sizes are usually correlated with increased x-ray intensity as a function of the input x-ray source power and the optic focusing capabilities. Increased power on the sample leads to improved analysis results. However, certain applications require small spot sizes for reasons other than intensity—smaller spot sizes enable higher spatial resolution and therefore more precise elemental mapping of the sample; as well as the ability to isolate certain features on a sample while preventing interfering fluorescence/diffraction returns from other adjacent features on the sample. Excitation beam spot sizes, though dramatically improved in the last few years, are still larger than many integrated circuit (IC) feature sizes now in use (e.g., scribe lines), and those planned for the “nanosystems” of the future.
Small spot sizes also enable small sample aperture sizes in, e.g., high-pressure on-line analysis systems, as discussed at length in the above-incorporated U.S. patent applications.
The monochromating optics discussed in the above-incorporated U.S. patent applications (e.g., doubly curved crystals) can achieve small spot sizes, but usually at the expense of aperture size, and (as fundamentally a device which is imaging the source) as a function of the x-ray source spot size, which may be too large. What is required, therefore, are techniques, methods and systems which exploit the benefits of x-ray monochromatization in e.g., XRF systems, while also providing small, intense, x-ray beam spot sizes.